Electric incandescent lamp



Feb. 28, 1961 E. H. WILEY meme INCANDESCENT LAMP Filed June 10. 1959 lnven tov'. Emm'e t t I-LWiLe b5 fizz; His A=tl7o neg.

ELECTRIC INQANDESCENT LAMP Emmett H. Wiley, Wiliowicir, Ohio, assignor to General Electric Company, a corporation of New York Filed June 10, 1959, Ser. No. 819,434

'3 Claims. (Cl. 313-42) My invention relates generally to electric incandescent lamps and particularly to lamps for use in light projectors.

Gas-filled projection lamps operate at considerably higher bulb and filament temperatures than ordinary incandescent lamps of comparable bulb size, and the hot convection currents arising from the filament impinge upon the region of the bulb above the filament and sweep down around the sides of the bulb. In spite of the gas filling which, at least during operation of the lamp, is above atmospheric pressure and tends to minimize vaporization of the filament, there is in fact considerable filament evaporation which condenses to form a 'black deposit on the buib. The black deposit causes increased absorption of heat bythe bulb so that the bulb becomes plastic and is blis'tered or 'bulged outwardly under the pressure of the internal gas filling. This blackening and deformation of the bulb renders the lamp useless well in advance of the end of the useful life of the filament and may seriously injure the projector in which the lamp is used.

Since conventional projectors employ a spherical mirror behind the lamp to direct light back through the bulb toward a condenser lens, most of the bulb surface in the vicinity of the filament has a high radiant flux passing through it. It has been proposed heretofore to employ anti-blackening screens or shields arranged to be located above the filament during operation of the lamp to intercept the material vaporized from the filament and to break up the convection currents. However, some of the vaporized material would still deposit on regions of the bulb surface where there was enough radiant flux absorbed to overheat the bulb.

In accordance with the present invention, I employ a reflector within the bulb and preferably in close proximity to the filament so that the bulb surface behind the reflector is not subjected to the high energy flux characterized by the use of an external mirror. This portion of the bulb then offers an ideal place to deposit the filament vapors carried by the gas stream. Accordingly, I employ, in combination with the said reflector, a heat deflecting member constructed and arranged to deflect the gas stream arising from the filament to the rear of the bulb behind the reflector. The blackening is thereby deposited on the surface of the bulb behind the reflector which is at a substantially lower temperature than the front side of the bulb and which does not serve for the emission of light therethrough so that blackening of that portion of the bulb is of no moment.

Further features and advantages of my invention will appear from the following detailed description of species thereof, and from the drawing wherein:

Fig. 1 is a front elevation of a projection lamp embodying the invention;

Fig. 2 is a cross-sectional view of the lamp taken along the line 2-2 of Fig. 1, with a diagrammatic showing of an associated condensing lens of a projector; and

tates Patent 9 ent brightness of the light source.

2,973,443 Patented Feb. 28, 1961 ice Figs. 3 and 4 are perspective views of modified forms of deflecting shields.

Referring to Fig. l, the lamp illustrated therein is adapted for use in a horizontal position and comprises a tubular glass bulb 1 containing a tungsten filament 2 herein illustrated as the planar type comprising a plurality of coiled wire sections arranged in staggered relation in closely parallel planes or, when desired, in a single plane. The filament 2. is arranged between longitudinally and horizontally extending support wires 3 and 4 sub stantially in a plane including the said wires and the axis of the bulb 1. The filament is electrically connected at its ends to wires 3 and 4 through spuds 5. Wire 3 is supported from, and electrically connected to, a leadin or contact pin 6 and is also connected to a second pin 7 through wire 8. Wire 4 is supported from andv electrically connected to pin 9, and is also connected to a second pin 10 (Fig. 2) through a conductor 11 which bridges pins 9 and 10 and which may be a fuse wire.

The filament 2 is supported at each end by a plurality of support wires 12 which engage the bight portions connecting successive coil segments of the filament and are supported from glass bridges 13 which are, in turn, supported from the support wires 3 and 4. The bulb 1 contains a filling of "inert gas, preferably nitrogen, at a substantial pressure, preferably about 600 mm. of mercury or higher, at room temperature.

In accordance with the invention, the lamp contains a reflector 14 located at one 'side of, or behind, the filament v2 and in close proximity thereto. As illustrated herein, the reflector an is of refractory :sheet metal, such as molybdenum, and is supported by a pair of support wires 15 which have their ends embedded in one of the bridges 13. The exact geometric shape and location of the reflector 14 is not critical; it is preferably of approximately the shape of the filament structure and is there fore of substantially rectangular shape. Such a reflector acts to direct light in a direction to increase the appar- The spaces between the turns and segments of the filament coils are at least partially filled in with light, the effect of which is to increase the black body characteristics of the surface and to thereby increase the apparentbrightness of the source. Such a reflector in close proximity to the incandescent coils requires no critical geometric shape or spacing in the optical system of the light projection device.

Further in accordance with the invention, the lamp contains a heat deflecting shield, herein illustrated as a foraminous screen 16, mounted along its longitudinal center line on the upper support wire 3 to be above the filament 2 in normal use of the lamp. The shield 16-is folded along its longitudinal center line to form two sides or panels 17 and 18 (Fig. 2). The panel 17 extends rearwardly in a plane substantially normal to the vertical plane including the wires 3, 4 and the bulb axis so as to be in a horizontal position in use of the lamp, whereas the panel 18 extends toward the front of the lamp in a plane inclined below the horizontal, at an angle of about 45 for instance.

The shield 16 shown in Figs. 1 and 2 may be formed from sheet nickel with a plurality of relatively large rectangular openings. However, other forms of deflecting shield may be employed, such as the expanded metal structure shown at 16a in Fig. 3, and the perforated sheet metal structure shown at 16b in Fig. 4.

With the lamp mounted in a projector behind a condensing lens 19 as shown in Fig. 2, the convection currents arising from the filament 2 strike the inclined side or panel 18 of the shield 16 and are deflected to the rear of the bulb behind the reflector 14. While a subthat a significant portion of it is directed to, and condenses upon, the bulb surface behind the reflector 14. Because of the presence of the reflector 14 within the interior of the bulb 1, the portion of the bulb behind the said reflector is not subjected to the high energy flux of prior art lamps used with an external mirror". Moreover, it does not serve for the emission of light from the lamp, and it is therefore ideally suited as a region toward which to direct the hot gas stream and in which to deposit tungsten vapors carried away from the filament 2 by the gas stream. By virtue of these coopera tive functions of the reflector 14 and the heat deflector 16, blistering of the surface of the bulb has been eliminated and the front of the bulb remains clean throughout the useful life of the lamp.

While I have described herein a preferred embodiment of the invention, it will be apparent to those skilled in the art that various modifications may be made in the arrangement of the filament, reflector and heat deflector Within the spirit and scope of the invention.

What I-claim as new and desire to secure'by Letters Patent of the United States is:

1. An electric incandescent lamp comprising a gasfilled glass bulb, a filament supported in said bulb, a reflector within said bulb adjacent to and at one side of said filament, and a heat deflector member in said bulb above said filament, said heat deflector member being inclined in a direction to deflect convection currents arising from said filament toward the bulb wall behind said reflector.

2. A horizontal burning projection. lamp comprising a tubular gas-filled glass bulb adapted to be horizontally disposed in normal use, a filament supported sub stantially in a vertical plane including the axis of said bulb, a reflector within said bulb substantially in a vertical plane adjacent to and to one side of the plane including said filament, and a heat deflecting shield extending longitudinally in said bulb above said filament and inclined in a direction to deflect convection currents arising from said filament toward the bulb wall behind said reflector.

3. A horizontal burning projection lamp comprising a tubular gas-filled glass bulb adapted to be horizontally disposed in normal use, an upper and a lower support member extending longitudinally and horizontally within said bulb, a planar filament mounted substantially in a vertical plane including said support members and the axis of said bulb, a substantially flat reflector within said bulb substantially in a vertical plane in close proximity to and to one side of the plane including said filament, and a heat deflecting shield extending longitudinally in said bulb above said filament and attached substantially along its longitudinal center line to the said upper support member, said shield being bent along its said center line to form two panels, one of said panels being in a substantially horizontal plane and extending laterally to-' ward the bulb wall behind said reflector, the other panel being in a plane inclined downward at an acute angle to the horizontal whereby to deflect convection currents arising from said filament toward the bulb wall behind said reflector.

References Cited in the file of this patent UNITED STATES PATENTS Wiley Sept. 15, 1959 

